Understanding catalytic hydrogenolysis of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) using carbon supported Ru catalysts

Catalytic Hydrogenation/Hydrogenolysis of 5‐Hydroxymethylfurfural to 2,5‐Dimethylfuran

“…When considering the economical feasibility of this process, it should also be kept in mind, that noble metal catalysts are more expensive, not necessarily, on the other hand, requiring high reaction temperature and pressure [20] contrary to alternative options. Monometallic Pd/C ( Table 1, entry 22) [44] and Ru/C ( Table 1, entry 18), [46] in which carbon facilitates electron transfer [38,44] have been quite good candidates for selective production of DMF, while Pt/SiO 2 and Pt/ Al 2 O 3 promoted mainly formation of products other than DMF from HMF at 180°C in 8 h in n-butanol under 10 bar hydrogen. [48] One challenge with monometallic catalysts is overhydrogenation, because these catalysts exhibit very high hydrogenation activity, as for example Ru/C.…”

“…PtÀ Ni/C XRD: shift to higher angle due to formation of Pt 6 Ni alloy and contraction of the lattice indicating formation of well-mixed bimetallic compounds [68] SAXS: formation of Pt [27] increased Cu reducibility due to spillover from Ru atoms, which is reduced [69] pyridine FTIR: low acidity XPS: low ratio of Cu 0 /(Cu 12 0.56 wt % Ru/HT [c] XRD: no Ru reflections H 2 TPR: small peak at 120 À 190°C related to Ru, the peak at 200-330°C indicate formation of RuO x which are interacting with support [70] 3.1 NA [36] 13 2 wt % Ru/MCS-30 [d] XRD: too small metal particle size to be detected nitrogen adsorption: specific surface area 2443 m 2 /g, pore width 2.3 nm XANES-EXAFS: 50 % Ru 0 and presence of RuO 2 confirmed small NA [46] 14 5 wt % Ru 10 wt % MoO x /C XPS: electron transfer from MoO x to Ru confirmed [71] and presence of Mo 5 + and Mo 4 + at BE of 232.0 and 229.6 eV [72] NH 3 TPD: peaks at 117°C-207°C correspond to weak acid sites H 2 TPR: peak at 180°C corresponds to reduction of RuO x to Ru 0 , [73] peak for Mo reduction at 350°C indicating that Ru facilitates easier reduction of Mo, [71] hydrogen spillover proposed facilitating also MoO x reduction [74] 1.8 680 [52] 15 3 wt % Pd/C XRD: graphitic carbon, and Pd(111) and Pd(220) planes found XPS: the presence of Pd and PdO confirmed suggesting electron interaction between them and enhancing hydrogenation [75] 2.6-3 NA [44] 16 PdAu 4 /graphitized carbon XPS: graphite phase, strong interaction between Pd and Au which could lead to charge transfer between them, Pd 0 72 %, Pd [76] TEM: d spacing of 0.215 nm corresponds to the wide-angle PXRD pattern at 2q 42.4°formation of Cu 3 Pd [77] XPS: Cu 2p 3/2 BE shifted to a lower value of 0.6 eV indicating a strong interaction between Cu and Pd, formation of Cu 3 Pd H 2 TPR: a peak at 420°C corresponds to reduction of one metal or metal alloy, weak adsorption of hydrogen atoms on Pd [78] XANES-EXAFS: the presence of Pd 0 and [83] XPS: high reducibility of Cu: Cu 0 82 % XANES: confirmation of a bimetallic CuÀ Ni EXAFS: incorporation of Ni 2 + into CuO framework [84] NA 3440 [42] 12 10 wt % Ni/TiO 2 XRD: anatase phase H 2 TPR: maximum at 420°C indicating weaker interaction of NiO x with titania support [85] TOF-SIMS: High ratio [86] overlapping reduction of Ni 2 + to Ni 0 at 300-350°C ...…”

“…Effect of metal loading and dispersion has been intensively investigated in HMF transformation to DMF. [38,40,44,51] In several cases it was reported that small metal particles and high metal dispersion facilitate high yields of DMF, [39,40,43,[45][46][47] while large metal particles facilitated hydrogenation of furan ring. [25,39,56] High metal loading (more than 3 wt % Pd in Pd/C) promotes dimer and ether formation in 2-propanol as well and overhydrogenation [44] ( Table 3, entry 15).…”

“…For example, a high metal dispersion in Ru/MCS-30 (microporous carbon) was beneficial for HMF transformation to DMF ( Table 3, entry 13). [46] Analogously small Ru particles supported Ru-HT facilitated high yield of DMF (Table 3, entry 12). [36] The metal particle sizes varied from 2.8 nm to 12.9 nm and the DMF yield decreased from 58 % to 35 % with increasing metal particle size.…”

“…Metal and solvent selection are also crucial and can determine both reaction rates and selectivity to DMF. Both noble [35,36,44,46] and transition metal catalysts [16,32,39] as well as bimetallic catalysts have been used in HMF transformations. The former ones are more expensive, requiring at the same time milder conditions, while transition metals are cheaper, operating, however, at harsher conditions.…”